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IP Routing Policy 103
Defining IP Prefix
A prefix list is identified by the IP prefix name. Each IP prefix can include multiple
items, and each item can specify the matching range of the network prefix forms.
The
index-number parameter specifies the matching sequence in the prefix list.
Perform the following configurations in system view.
During the matching, the router checks list items identified by the index-number in
the ascending order. If only one list item meets the condition, it means that it has
passed the ip-prefix filtering (and does not enter the testing of the next list item).
If more than one IP prefix item is defined, then the match mode of at least one list
item should be the permit mode. The list items of the deny mode can be defined
to rapidly filter the routing information not satisfying the requirement, but if all
the items are in the deny mode, no route will pass the ip-prefix filtering. You can
define an item of permit 0.0.0.0/0 greater-equal 0 less-equal 32 after the multiple
list items in the deny mode to let all the other routes pass.
Configuring for Filtering Received Routes
Perform the following configuration in routing protocol view.
Define a policy that filters the routing information that does not satisfy the
conditions and receives routes with the help of an ACL or address prefix-list. The
filter-policy gateway command specifies that only the update packets from a
specific neighboring router will be received.
Table 104 Defining Prefix-list
Operation Command
Define a prefix list ip ip-prefix ip-prefix-name [
index index-number ] { permit |
deny } network len [
greater-equal greater-equal ] [
less-equal less-equal ]
Remove a prefix list undo ip ip-prefix ip-prefix-name
[ index index-number | permit |
deny ]
Table 105 Configuring Filtering for Received Routes
Operation Command
Configure to filter the received routing
information distributed by the specified
address
filter-policy gateway
ip-prefix-name import
Cancel the filtering of the received routing
information distributed by the specified
address
undo filter-policy gateway
ip-prefix-name import
Configure to filter the received global routing
information
filter-policy { acl-number |
ip-prefix ip-prefix-name } [
gateway ] import
Cancel the filtering of the received global
routing information
undo filter-policy { acl-number |
ip-prefix ip-prefix-name } [
gateway ] import